U.S. Pat. No. 3,125,751 (Winters) discloses alarms for indicating to operating personnel when a projecting portion of a vehicle or other apparatus too closely approaches an energized electric power line.
U.S. Pat. No. 6,600,426 (Sacks et al.) discloses an alarm system for detecting an warning of the risk of shock and electrocution. The alarm system is adapted for use with mobile construction equipment, e.g., cranes, trucks, etc., that can be used around overhead power transmission lines. The alarm system has a sensor that detects the presence of outside power at the equipment where current is flowing therethrough to the ground. The sensor preferably includes a conductor and an inductive sensor such as a current transformer which limits the output signal on its low side that is sent to an alarm unit. In this manner, the system purports to continue to properly function despite the presence of large voltages at the equipment such as when the equipment contacts a high voltage power transmission line. The sensor can include a cable that provides a path of least resistance for current flowing through the equipment which can be detected by the sensor. Preferably, the cable is attached across a moving joint of the equipment where potential differences readily can be found. Alternatively, the conductor can be a portion of the equipment itself, through which current flows with the sensor detecting the flow through the equipment portion.
U.S. Pat. No. 6,853,307 (Nickerson) discloses a high-voltage-proximity warning system that has a local panel for being positioned in or about a cab of heavy equipment or other vehicle, a remote panel in predetermined electrical communication with the local panel and one or more proximity antennas for being positioned selectively on the vehicle in predetermined electrical communication with the local panel. The local panel is adapted to be push-button operable conveniently by an operator with gloved hands in a position where it is readily visible and easily connectable electrically to the remote panel and to the one or more proximity antennas. The remote panel is adapted to be positioned on or off of the vehicle where it can be protected for supportive operation and accessed for plural electrical connection to electrical devices that can include an electrical-source terminal, to speakers, and to warning and alarm communication devices. A method for use includes placing the local panel suitably for access by the vehicle operator in or about the cab, placing the remote panel suitable for access by a user technician in the vicinity of the local panel, setting control levels of high-voltage sensing an alarm control by the user technician, adjusting the alarm setpoint by the operator within the control levels set by the user technician in a configuration mode and connecting the system to an ignition terminal and to the communication devices which can be customized for use conditions.